AHSGE: Science Introduction to Chemistry

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AHSGE Science Introduction to Chemistry

• The Periodic Table

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The Periodic Table

• In this section you will
• Describe the Purpose of the Periodic Table
• Determine General Information about the Elements
• Determine Electron Configurations of Elements
• Determine Reactivity of Groups of Elements
• Determine Relative Size of Atoms
• Classify Elements by Metals, Nonmetals, and Noble
  Gases

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Purpose of the Periodic Table
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Home

• There are approximately 109 atoms each with its
  own atomic number, mass, and properties. How
  would you keep track of all the information about
  all the atoms?

• Tables are used to organize information because
  they can present a large amount of information in
  a compact form.
• The Periodic Table is a collection of
  information about the elements.
• Click on the picture (right) and print a copy
  for reference.

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Purpose of the Periodic Table
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• You can get a tremendous amount of information
  from the Periodic Table if you know how to read
  it.

• The Periodic Table can be used simply as a list
  of the elements from which you can get general
  information about the elements such as name,
  symbol, atomic number mass.

• If you know the Atomic Numberand Atomic Mass,
  you can determinethe number of Protons,
  Neutrons, and Electrons.

6 C Carbon 12.0
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Purpose of the Periodic Table
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• The Periodic Table, however, is more than just a
  simple list of the elements.

• It is organized so that atoms with similar
  properties are grouped together and differences
  between elements can be predicted based on their
  location.

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Purpose of the Periodic Table
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• Rows on the Periodic Table are called Periods.
  Gradual changes occur as you move across a period.

• Columns on the Periodic Table are called Groups.
  The elements in a group have similar properties.

Group1
8
Period 1
2
3
4
5
6
7
Period 2
Period 3
Period 4
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Purpose of the Periodic Table
Home

• In the following sections you will learn to use
  the periodic table to get the following types of
  information about the elements.

• General information Atomic Number, Mass, Name,
  Symbol, Number of Subatomic Particles.
• Electron Configuration
• Reactivity
• Size
• Type of Element Metal, Nonmetal, Noble Gas

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General Information about the Elements
Home

• The Periodic Table provides general information
  about the elements such as Name, Symbol, Atomic
  Number, Atomic Mass.

• From this, the number of Protons, Neutrons,
  Electrons in an unreacted atom can be determined.
• On every Periodic Table there is a key that
  explains how to interpret the information.

Key
Atomic Number(Protons)
Symbol
11 Na Sodium 23.0
Atomic Mass(Protons Neutrons)
Name
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General Information about the Elements

• Determine the indicated information about the
  unreacted element shown below.

4 Be Beryllium 9.0
Beryllium
Be
4
9.0
4(atomic number)
5(atomic mass atomic number)
4(same as protons in unreacted atom)
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General Information about the Elements

• What element has 14 protons?

Silicon

• What element has the symbol Fe?

Iron

• What is the mass of Chlorine?

35.5 AMUs
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General Information about the Elements

• The last question may have made you wonder How
  can Chlorine have a mass of 35.5?

17 Cl Chlorine 35.5

• Chlorine has 17 protons. So does it have18 and a
  half neutrons?
• No, you cant have half of a subatomic particle.
• The extra 0.5 is due to the existence of various
  isotopes of Chlorine.
• Chlorine has a mass of 35.5 because about 75 of
  Chlorine atoms have 18 neutrons (Cl 35) and 25
  have 20 neutrons (Cl 37). A weighted average of
  the different isotopes gives a mass of 35.5.

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General Information about the Elements
Home

• The Periodic Table can be used simply as list of
  the elements.

• From this list you can get information about an
  element such as
• Name
• Symbol
• Atomic Mass
• Atomic Number
• Number of Protons, Neutrons, Electrons

11 Na Sodium 23.0
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Electron Configurationsof the Elements
Home

• The Periodic Table is not just a list of the
  elements. If general information was all we
  wanted to convey, then a simple rectangular table
  would do the job.

• You have probably noticed the unusual shape of
  the periodic table. There must be a reason it
  has this shape.

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Electron Configurationsof the Elements

• We already mentioned that the Periodic Table
  groups together elements with similar properties.

• Do you see anything similar about the elements in
  a particular group? (Remember, groups columns)

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Electron Configurationsof the Elements

• On the surface, the elements in a group dont
  seem to have much in common.

• The members of group 1 for example have very
  different atomic numbers, masses,and numbers of
  subatomic particles. So, what makes these
  elements similar?
• Since the number of particles isnt similar, then
  maybe their similarity has something to do with
  the structure of the atoms.
• Since protons and neutrons are always in the
  nucleus, any structural similarities must be due
  to electron location.

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Electron Configurationsof the Elements

• Lets draw a model of the first three atoms in
  Group 1 to check for similarities.

• Refer to the model of the atom shown below to
  complete your drawings. (You can put a maximum
  of 2 electrons in each orbital)

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Electron Configurationsof the Elements

• Hydrogen has 1proton and therefore 1 electron

• The electron will go in the first energy level in
  the S orbital.

Hydrogen
1 Electron - 1st Energy Level 1e- in S Orbital
nucleus
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Electron Configurationsof the Elements

• Lithium has 3 electrons

2 Electrons - 1st Energy Level 2e- in S Orbital
Lithium
1 Electron - 2nd Energy Level 1e- in S Orbital
nucleus
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Electron Configurationsof the Elements

• Sodium has 11 electrons

2 Electrons - 1st Energy Level 2e- in S
Orbital
Sodium
8 Electrons - 2nd Energy Level 2e- in S
Orbital 6e- in P Orbitals
nucleus
1 Electron - 3rd Energy Level 1e- in S Orbital
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Electron Configurationsof the Elements

• Did you notice any similarities in the first 3
  elements of Group 1?

Hydrogen

• The elements in Group 1 have one electron in
  their outermost energy level.
• Remember, atoms want to react to fill the S P
  orbitals of their outer energy levels
• So, atoms with the same number of electrons in
  their outer level react similarly.

Lithium
Sodium
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Electron Configurationsof the Elements

• Lets draw the first 2 atoms from Group 7 to see
  if the trend holds.

Fluorine

• The elements in Group 7 have 7electrons in their
  outermost energy level.
• Fluorine has 9 electrons 2e- in 1st level
  - S orbital 7e- in 2nd level - 2 in S 5 in P
  orbitals
• Chlorine has 17 electrons 2e- in 1st level
  - S orbital 8e- in 2nd level - 2 in S 6 in P
  orbitals 7e- in 3rd level - 2 in S 5 in P
  orbitals
• These elements react similarly because they have
  7 electrons in the S P orbitals of their outer
  level.

Chlorine
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Electron Configurationsof the Elements

• Draw the first three atoms from Group 8?

Helium

• The elements in Group 8 have eight electrons in
  their outer level.

Neon

• Helium has 2 electrons 2e- in 1st level -
  S orbital
• Neon has 10 electrons 2e- in 1st level - S
  orbital 8e- in 2nd level - 2 in S 6 in P
  orbitals
• Argon has 18 electrons 2e- in 1st level -
  S orbital 8e- in 2nd level - 2 in S 6 in P
  orbitals 8e- in 3rd level - 2 in S 6 in P
  orbitals
• Group 8 atoms have the S P orbitals of their
  outer level full.

Helium is an exception. It doesnt have eight
electrons in its outer level because its outer
level is the 1st which can only hold two.
Argon
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Electron Configurationsof the Elements

• Answer the following questions to review.

Group

• The atoms in a (Period / Group) have similar
  properties.
• List an element that is similar to Oxygen.
• Why do atoms in a group react similarly?

Sulfur, Selenium, or Tellurium
The atoms of a group are similar because they
have the same number of electrons in the S and P
orbitals of their outer energy level.
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Electron Configurationsof the Elements

• Knowing where electrons are located is key to
  determining how an atom will react.

• To this point, you have used the model below to
  determine the location of an atoms electrons.

• You can get the same information from the
  Periodic Table if you know how to interpret it.

Energy Levels
Orbitals
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Electron Configurationsof the Elements

• We will compare the old model to the Periodic
  Table by placing electrons in the energy levels
  and orbitals one at a time.

• First, you need to know two things about the
  structure of the Periodic Table.

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Electron Configurationsof the Elements

• Periods (rows) represent Energy Levels.

Keep in mind This slide shows only a portion
of the Periodic Table.The trends you see
continue down through the entire table. Next we
will compare our old model of the atom to the
Periodic Table but we will only be concerned with
the first 21 atoms.

• Groups (columns) represent Orbitals.

SOrbitals
POrbitals
Level 1
Level 2
DOrbitals
Level 3
Level 4
FOrbitals
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Electron Configurationsof the Elements
Model of the Atom
Where will the 13th electron be located? The S
orbital of the third level is now full.
For an atom with 2 electrons Helium. Where would
the 2nd electron be located?
Notice the S P orbitals of the outer level are
full for Helium.
Where would Lithiums third electron be located?
(The first 2e- are located as previously shown.)
Where would Berylliums fourth electron be
located?
Where would Borons fifth electron be located?
The S orbitals of the 2nd level are full.
Lets skip to Neon with 10 e-. Where will Neons
last 5 electrons be located?
Notice, the S P orbitals of Neons outer energy
level are full.
Where will the 11th and 12th electrons be
located? The second energy level is now full.
Lets skip to Argon with 18 e-. Where will
Argons last 5 electrons be located?
Notice, the S and P orbitals of Argons outer
energy level are full.
Where would the 19th and 20th electrons be
located? Look at the Model the Periodic Table.
The Model suggests the D orbitals but the
Periodic Table says the S orbitals of the 4th
level.
The Periodic Table is right. The 19th 20th
electrons are in the S orbitals of the 4th
energy level.
Where will the 21st electron go? The Periodic
Table indicates the D orbitals of the 3rd energy
level.
The Periodic Table gives the same information
about electron location as the Model only better.
The Model is accurate for the first 18 elements
only, but the Periodic Table works for all the
elements.
Youre probably wondering why the electrons dont
fill their energy levels and orbitals according
to the Model. Why do they jump around?
Electrons want to use the least amount of energy
possible as they circle the nucleus. The amount
of energy is determined by both the Energy Level
and the Orbital.
It takes more energy to fly in a more distant
level. So, electrons will fill lower levels
before they fill higher levels.1 ? 2 ? 3 ? etc.
It takes more energy to fly in a more complex
orbital (flight pattern). So, electrons fill the
simple orbitals firstS ? P ? D ? F
When you consider energy requirements for both
the Energy Level and the Orbital at the same
time, you begin to see this jumping around
Once the P orbitals of the 3rd level were filled,
there was a choice between the S orbitals of the
4th level and the D orbitals of the 3rd level.
The S orbital of the 4th level had lower energy
requirements. Although the 4th level is more
distant, the S orbital was much less complex.
Once the S orbital of the 4th level was full, the
choice was between the D orbitals of the 3rd
level and the P orbitals of the 4th level.
The D orbitals of the 3rd level had lower energy
requirements. Although the D orbitals are more
complex, the 3rd level is closer than the 4th
level.
The Periodic Table can be used to determine the
number and location of the electrons for any
element.
The location of an elements electrons is called
the Electron Configuration. The electron
configuration of an element determines how the
atom will react.
Watch how electrons fill their energy levels and
orbitals on both the Model and Periodic Table
Lets start with an atom that has 1 electron
Hydrogen.
Level 1S Orbital
Level 1S Orbital
Level 2S Orbital
Level 2S Orbital
Level 2P Orbital
Level 2P Orbital
Level 3S Orbital
Level 3P Orbital
Level 3P Orbital
Level 4S Orbital
Level 3D Orbital
The Periodic Table
Period 1S Group
Period 1S Group
Period 2S Group
Period 2S Group
Period 2P Group
Period 2P Group
Period 3S Group
Period 3P Group
Period 3P Group
Period 4S Group
D Group
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Electron Configurationsof the Elements

• In the previous slides you used the Periodic
  Table to determine electron configurations.

• Electron configuration is the location of an
  atoms electrons.
• Showing electron configuration by drawing models
  of the atoms can be a very tedious process.

• Consequently, a short-hand notation was
  developed.
• The next slide will show you how to write
  electron configurations with this method.

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Electron Configurationsof the Elements

• Write the electron configuration for Fluorine.

Determine the number of electrons in an atom of
Fluorine
Use the Periodic Table to locate Fluorines 9
electrons.Periods Energy LevelsGroups
Orbitals.
1 refers to the Energy Level.S refers to the
Orbital2 is the number of electrons in that
orbital.
We located 2 of Fluorines 9 e-. We have 7 left
to locate. Where do we go next?
We just placed 2 more electrons in the S orbital
of the 2nd level. 2 S 2
We have now located 4 of Fluorines 9
electrons.Where do we go next?
The P orbitals of the 2nd level can hold a
maximum of 6 e-. We only have 5 e- left to
place.
Fluorines last 5 electrons are located in the P
orbitals of the 2nd level.
The Electron Configuration for Fluorine is 1S2
2S2 2P5We located all 9 electrons.
Fluorine 9e-
1 S 2
2 S 2
2 P 5
The Periodic Table
Period 1S Group
Period 2S Group
Period 2P Group
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Electron Configurationsof the Elements

• Write the electron configuration for Calcium.

Calciums next 6 electrons were just put in the
P orbitals of the 2nd level. 2 P6
We just found a spot for 6 more electrons in the
P orbitals of the 3rd level.3P 6
18 of Calciums 20 electrons have now been
accounted for.Where will the last 2 electrons
be located?
Determine the number of electrons in an atom of
Calcium
Use the Periodic Table to locate Calciums 20
electrons.Periods Energy LevelsGroups
Orbitals.
1 refers to the Energy Level.S refers to the
Orbital2 is the number of electrons in that
orbital.
We located 2 of Calciums 20 e-. We have 18 left
to locate. Where do we go next?
We just placed 2 more electrons in the S orbital
of the 2nd level. 2 S 2
We have now located 4 of Calciums 20
electrons.Where do we go next?
2 more electrons were just placed in the S
orbital of the 3rd level. 3S2
That takes care of 12 electrons.We have 8 more
to locate.What is our next step?
Calciums last 2 e- were placed in the S orbital
of the 4th level.4S 2
The Electron Configuration for Calcium is 1S 2
2S 2 2P 6 3S 2 3P 6 4S 2 All 20 e-
have been located.
If you can determine the electron configuration
for calcium then you can do any element before
calcium.
Electrons will follow the same pattern in filling
Energy Levels and Orbitals. Its a matter of how
many e- you need to place.
We have accounted for 10 of Calciums 20 e-.
Where do we go from here?
Calcium 20 e-
1S 2
2S 2
2P 6
3S 2
3P 6
4S 2
The Periodic Table
Period 1S Group
Period 2S Group
Period 2P Group
Period 3S Group
Period 3P Group
Period 4S Group
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Electron Configurationsof the Elements
Home

• Write electron configurations for the elements.

4 e - 1S 2 2S 2
Beryllium Carbon Magnesium Sulfur Potassi
um
6 e - 1S 2 2S 2 2P 2
12 e - 1S 2 2S 2 2P 6 3S 2
16 e - 1S 2 2S 2 2P 6 3S 2 3P 4
19 e - 1S 2 2S 2 2P 6 3S 2 3P 6 4S 1
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Reactivity of Groups of Elements
Home

• In the last section you found that the Periodic
  Table could be used to determine the location of
  an atoms electrons. (Electron Configuration)

• Electron Configuration is important because it
  determines how an atom will react.
• Remember, a chemical reaction is an atom gaining
  or losing electrons.
• Atoms react is to fill the S and P Orbitals of
  their outer Energy Level making them more stable.
• The Periodic Table can be used to determine what
  Groups of elements will do when they react.

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Reactivity of Groups of Elements

• What will the atoms in Group 1 do when they react?

The elements in Group 1, like Lithium, all have 1
electron in the S P Orbitals of their outer
Energy Level.
Atoms want to react to fill the S P orbitals of
their outer level. Lithium could do this in one
of two ways.
There are 7 empty slots in the S P orbitals of
Lithiums 2nd energy level.
So, one way Lithium could fill the S P
orbitals of its outer level would be to get 7
more electrons.
Another option would be for Lithium to lose the 1
e- that is in the 2nd level.
If Lithium lost an electron, its outer level
would be the 1st and the 1st level is already
full.
Would it be easier for Lithium to gain 7
electrons or to lose 1 electron?
When Lithium reacts it will lose 1e- and become a
Lithium Ion with a 1 charge.Li 1
Since all the elements in Group 1 have one
electron in their outer level, they will all
react like Lithium.
The elements in Group 1 all tend to lose 1
electron and become ions with a 1 charge.
Lithium
- Note -Atoms cant gain electrons unless they
can find another that is willing to give.Atoms
cant lose electrons unless they can find another
that is willing to gain.
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Reactivity of Groups of Elements

• What will the atoms in Group 7 do when they react?

Fluorine
The elements in Group 7 all tend to gain 1
electron and become ions with a -1 charge.
It would it be easier for Fluorine to gain 1
electron than to lose 7 electrons?
When Fluorine reacts it will gain 1e- and become
a Fluorine Ion with a -1 charge.F -1
Since all the elements in Group 7 have seven
electrons in their outer level, they will all
react like Fluorine.
The elements in Group 7, like Fluorine, all have
7 electrons in the S P Orbitals of their outer
Energy Level.
Atoms want to react to fill the S P orbitals of
their outer level. Fluorine could do this in one
of two ways.
There are 7 electrons in the S P orbitals of
Fluorines 2nd energy level.
So, one way Fluorine could fill the S P
orbitals of its outer level would be to lose
those 7 electrons.
Another option would be for Fluorine to gain 1
electron and fill the last empty slot in the 2nd
level.
- Note -Atoms cant gain electrons unless they
can find another that is willing to give.Atoms
cant lose electrons unless they can find another
that is willing to gain.
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Reactivity of Groups of Elements

• What will the atoms in Group 8 do when they react?

The elements in Group 8, like Neon, all have 8
electrons in the S P Orbitals of their outer
Energy Level.
Atoms want to react to fill the S P orbitals of
their outer energy level.
There are 8 electrons in the S P orbitals of
Neons 2nd energy level.
The S P orbitals can only hold 8 electrons.
So, Neons outer energy level is already full.
Neon will NOT gain or lose electrons because the
S P orbitals of its outer level are already
full.
Having full S P orbitals in the outer level
makes an atom more stable. So, Neon will not
react.
Because of their electron configuration all the
elements in Group 8 are unreactive just like
Neon.
The elements in Group 8 are called the Inert
Gases. (Inert means unreactive.)
Neon
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Reactivity of Groups of Elements

• What will the atoms in Group 2 do when they react?

• The elements in Group 2 have 2 e- in their outer
  level. They tend to lose those two electrons. In
  the process, the atoms become positively charged
  ions. Since they lose 2 e- they take on a 2
  charge.

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Reactivity of Groups of Elements

• What will the atoms in Group 6 do when they react?

• The elements in Group 6 have 6 e- in their outer
  level. They tend to gain two electrons. In the
  process, the atoms become negatively charged
  ions. Since they gain 2 e- they take on a -2
  charge.

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Reactivity of Groups of Elements

• We just used the Periodic Table to determine how
  groups of elements will react.

1
-2
-1
2
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Reactivity of Groups of Elements

• The Periodic Table can also be used to judge how
  reactive each group will be.

• In other words Which Groups contain the most
  reactive elements? What Groups are more stable?

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Reactivity of Groups of Elements

• Which Group is the least reactive? Why?

• The elements in Group 8 are the least reactive
  because the S P orbitals of their outer energy
  level is already full. They dont need to gain
  or lose electrons. They are stable.

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Reactivity of Groups of Elements

• Which two Groups are the most reactive? Why?

• Groups 1 7 are the most reactive because they
  are only 1 e- away from filling the S P
  orbitals of their outer level. When Group 1
  loses one and Group 7 gains 1. The atoms will be
  more stable.

Its like being on a long car trip. The closer
you are to your destination, the worse you want
to get there. Groups 1 and 7 are only 1
electron away from getting what they want so they
are very reactive.
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Reactivity of Groups of Elements

• Which Groups are the next most reactive? Why?

• Groups 2 6 are next most reactive because they
  are 2 e- away from filling the S P orbitals of
  their outer level. When Group 2 loses two and
  Group 6 gains two. The atoms will be more stable.

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Reactivity of Groups of Elements
Home

• As we move toward the edges of the Periodic Table
  the elements get more reactive.

• As we move toward the middle of the Periodic
  Table, the elements get more stable

• The elements in Group 8 are the least reactive.

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Determine Relative Size of the Atoms
Home

• The Periodic Table can also be used to predict
  relative sizes of the atoms.

• In other words, if you pick out two elements you
  could tell the larger from the smaller by their
  positions on the Periodic Table.
• Remember, the protons and neutrons of an atom are
  located in a very small area (the nucleus) so the
  size of an atom is mostly dependent on the
  location of the electrons (energy levels).
• In this section, think about the size of an
  atom in terms of the distance from the center of
  the nucleus to the outer energy level.

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Determine Relative Size of the Atoms

• What happens to the size of the atoms as you move
  down a group on the Periodic Table?

Hydrogen
As you move down a groupthe outer energy
levelincreases, so size increases as well.
Hydrogens outer level 1stLithiums outer
level 2ndSodiums outer level 3rdetc.
Atoms increase in size as you move down a group.
Lithium
Sodium
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Determine Relative Size of the Atoms

• What happens to the size of the atoms as you move
  across a period to the right on the Periodic
  Table?

Period2
Lithium
Fluorine
3 Protons
9 Protons
2nd Energy Level
2nd Energy Level
Atoms get smaller as you move across a period (to
the right) on the Periodic Table.
This doesnt seem to makemuch sense. How can
the atoms get smaller when they have more
subatomic particles?
Before we answer that, we need to answer another
question. What keeps electrons in orbit around
the atom?
The positively charged protons in the nucleus
pull the negatively charged electrons. Opposites
Attract
How many positive charges (protons) do Lithium
and Fluorine have in their nuclei?
In what Energy Level are the outer electrons for
Lithium and Fluorine?
The protons for both Lithium and Fluorine are
pulling on electrons that are in the 2nd Energy
Level.
Fluorine has 9 protons with which to pull while
Lithium has only 3 protons.So
Fluorine can pull the electrons harder and
therefore closer. This makes Fluorine smaller
than Lithium.
Atoms get smaller as you move to the right on a
period because
You are adding more protons which gives a greater
pull while the electrons are added to the same
energy level.
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Reactivity of Groups of Elements
Home

• Atoms get larger as we move down a group.

• Atoms get smaller as we move to the right across
  a period.

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Metal, Nonmetalsand Noble Gases
Home

• Our final use for the Periodic Table is to
  classify elements as Metals, Nonmetals, and Noble
  Gases.

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Metal, Nonmetalsand Noble Gases

• The Noble Gases are located in Group 8.

We previously discussed the properties of this
Group of elements. We called them the Inert
Gases.
The terms Inert Gases and Noble Gases can be use
interchangeably.
The Noble Gases are similar because they have a
similar electron configuration.
The Noble Gases all have full S P orbitals in
their outer level. This configuration makes them
stable.
Because of this stable configuration, the Noble
Gases do not react with other elements.
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Metal, Nonmetalsand Noble Gases

• Notice the thick stair-stepline on the table.

This line separates the Metals from the
Nonmetals
The Nonmetals are located above and to the right
of the line
When Nonmetals react they often gain electrons
and become negatively charged ions.
The Metals are located below and to the left of
the line.
When Metals react they tend to give up electrons
and become positively charged ions.
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Metal, Nonmetalsand Noble Gases
Home

• Identify the Metals, Nonmetals, and Noble Gases.

Noble Gases
Nonmetals
Metals
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AHSGE Science Introduction to Chemistry

• You have Completed
• The Periodic Table